The present disclosure relates generally to infrared light reflecting film. The present invention more particularly relates to infrared light reflecting film that includes a cholesteric liquid crystal layer.
Dyed and vacuum-coated plastic films have been applied to windows to reduce heat load due to sunlight. To reduce heat load, solar transmission is blocked in either the visible or the infrared portions of the solar spectrum (i.e., at wavelengths ranging from 400 nm to 2500 nm or greater.)
Primarily through absorption, dyed films can control the transmission of visible light and consequently provides glare reduction. However, dyed films generally do not block near-infrared solar energy and consequently are not completely effective as infrared light reflecting film or solar control films. Dyed films also often fade with solar exposure. In addition, when films are colored with multiple dyes, the dyes often fade at different rates, causing an unwanted color changes over the life of the film.
Other known window films are fabricated using vacuum-deposited grey metals, such as stainless steel, inconel, monel, chrome, or nichrome alloys. The deposited grey metal films offer about the same degrees of transmission in the visible and infrared portions of the solar spectrum. As a result, the grey metal films are an improvement over dyed films with regard to solar control. The grey metal films are relatively stable when exposed to light, oxygen, and/or moisture, and in those cases in which the transmission of the coatings increases due to oxidation, color changes are generally not detectable. After application to clear glass, grey metals block light transmission by approximately equal amounts of solar reflection and absorption.
Vacuum-deposited layers such as silver, aluminum, and copper control solar radiation primarily by reflection and are useful only in a limited number of applications due to the high level of visible reflectance. A modest degree of selectivity (i.e., higher visible transmission than infrared transmission) is afforded by certain reflective materials, such as copper and silver.
There is a need for improved infrared light reflecting film or solar control film that has a high visible light transmission and substantially blocks infrared radiation.